Recently, attention has been concentrated, in the paint industry to a resinous copolymer of cellulose acetate butyrate (hereinafter referred to CAB) and vinyl monomer, having excellent drying properties, hardness and other desired properties.
To obtain such resinous copolymer, various methods have been proposed including:
(1) A method wherein CAB is directly copolymerized with vinyl monomer(s), using an organic peroxide as a polymerization initiator, as shown, for example, in Japanese Patent Application Kokai Nos. 115126/74, ibid 133472/80, ibid 54301/80, Japanese Patent Publication Nos. 37683/75, ibid 5659/76, ibid 5660/76 and ibid 2978/83. PA0 (2) A method wherein specified amounts of acid, acid anhydride, acid chloride or isocyanate are first reacted with the hydroxyl groups of CAB, thereby introducing to the CAB molecule mercapto groups, a group from which hydrogen may be easily drawn or unsaturation bonding, and then vinyl monomer(s) is (are) graft-polymerized, as given, for example, in Japanese Patent Application Kokai Nos. 80192/73; ibid 48030/75; ibid 48031/75; Japanese Patent Publication No. 8105/80. PA0 (3) A method wherein graft polymerization is carried out using a Co.sup.66 or Ce.sup.+++ salt. PA0 (1) vinyl monomers such as styrene, vinyl toluene, .alpha.-methyl styrene, vinyl acetate, acrylonitrile, methacrylonitrile and the like, PA0 (2) alkyl or cycloalkyl esters of acrylic or methacrylic acid such as methyl acrylate, methyl methacrylate, ethyl acrylate, ethyl methacrylate, n-butyl acrylate, n-butyl methacrylate, iso-butyl acrylate, iso-butyl methacrylate, t-butyl acrylate, t-butyl methacrylate, cylcohexyl acrylate, cyclohexyl methacrylate, 2-ethyl hexyl acrylate, 2-ethyl hexyl methacrylate, lauryl acrylate, lauryl methacrylate, stearyl acrylate, stearyl methacrylate, and the like, PA0 (3) hydroxyalkyl esters of acrylic or methacrylic acid such as 2-hydroxyethyl acrylate, 2-hydroxyehtyl methacrylate, hydroxypropyl acrylate, hydroxypropyl methacrylate and the like, PA0 (4) .alpha.,.beta.-ethylenically unsaturated carboxylic acids such as acrylic acid, methacrylic acid, itaconic acid, crotonic acid and the like, PA0 (5) acrylamides or methacrylamides such as acrylamide, methacrylamide, N-methylacrylamide, N-ethyl methacrylamide, N-methylol acrylamide, N-methylol methacrylamide, N,N-dimethyl acrylamide, N,N-dimethyl methacrylamide, N-n-butoxymethyl acrylamide and the like, PA0 (6) glycidyl group bearing vinyl monomers such as glycidyl acrylate, glycidyl methacrylate, allyl glycidyl ether and the like.
However, in any of the known methods, there is a serious drawback in that the grafting rate is extremely low. Therefore, when the resinous solution thus obtained is applied and dried, there always results a coating with white blooming.
Moreover, the resinous product has poor compatibility with other resins as, for example, acrylic resins, polyester resins, high styrene containing acrylic resins and the like, and the product has only limited solubility in various solvents, such as toluene, xylene and other paint-use solvents.
The above is especially true when CAB is reacted with maleic anhydride or maleic acid, in that no CAB graft copolymer suitable for paint use has been obtained. The inventors, having paid attention to the fact that CAB has a number of ester bondings, such as an acetate and a butyrate, besides hydroxyl groups, have endeavored to utilize these functional groups for the introduction of polymerizable unsaturation bonding and have succeeded in finding an ingenious way of reacting cellulose ester and mono- or diester of maleic or fumaric acid for that purpose.
On the present basis of this finding, the invention has been made.